1. Field of the Invention
The present invention relates to a sealing structure. More particularly, the present invention relates to a sealing structure providing waterproof function for electric devices and connectors.
2. Description of the Conventional Art
Recently, waterproof connectors used in an electric device such as a mobile phone or the like and a wire harness used in an automobile or the like have been miniaturized and high waterproof function has been required at the same time.
In order to provide waterproof function for an electric device having a plurality of spaces therein, it is necessary to airtightly seal respective housings that define individual spaces and to connect electrically devices in the respective spaces by means of flexible wiring boards or the like.
In this case, there has been proposed a way that terminals are provided on the wall surfaces of the housings defining the spaces and the terminals are connected by the wiring materials, or another way that the wiring materials are extended through the walls of the housings and the gaps produced between the wiring materials and the housings are filled with an adhesive agent or the like.
However, the former structure of providing the terminals on the wall surfaces of the housings has a problem that the equipment becomes larger in size, and the latter structure of filling the gaps produced between the wiring materials and the housings with the adhesive agent or the like has a problem that disassembly and reassembly is difficult.
Consequently, there has been proposed another structure of forming sealing members integrally with a flexible wiring board as shown in FIGS. 7 and 8 (Japanese unexamined patent publication Nos. 2003-142836 and 2004-214927).
FIG. 7 shows a structure in which sealing members 301 having frame shapes corresponding to the shape of respective housings (not shown) are formed integrally with a flexible wiring board 100. The flexible wiring board 100 extends through the respective sealing members 301, and electric devices are mounted in regions surrounded by respective seal members 301.
Further, FIG. 8 shows another structure in which sealing members 303 having a bush shape are formed integrally with a flexible wiring board 100. The sealing members 303 are attached to an insertion holes provided in respective housings (not shown), and connectors 304 provided at both ends of the flexible wiring board 100 are electrically connected to the electric devices in the housings.
Further, there has been proposed still another structure as shown in FIG. 4, in combination of the structures shown in FIGS. 7 and 8, in which a frame-shaped seal 31 and a bush-shaped seal 32 are integrally formed at one side and the other side of the flexible wiring board 1 respectively.
However, the below mentioned problems arises as shown in FIGS. 5 and 6 which are sectional views taken along lines A-A in FIG. 4.
The flexible wiring board 1 is normally provided with the following structure. A printed wiring layer 12 (circuit pattern) made from a copper foil is bonded fixedly to one surface of a base substrate 11. The base substrate 11 is made of an elastic material such as polyimide, polyamide, polyester, liquid crystal polymer or the like. Further, a cover film 13 is formed on the surface of printed wiring layer 12 to protect the surface thereof. The cover film 13 is formed from the same material as the elastic material used for the base substrate 11. Thus, the printed wiring layer 12 is structured so as to be sandwiched between the base substrate 11 and the cover film 13. Further, molding pressure and heating are needed when the seal member 3 is integrally formed on the flexible wiring board 1. As a result, there arises a problem that the printed wiring layer 12 as shown in FIG. 5 comes under thermal influence and is deformed as shown in FIG. 6. Consequently, the seal member 3 also comes under thermal influence, and the sealing capability is lowered at that portion. As a result, the bonding between the housing and the sealing member 3 cannot work successfully, thereby causing leakage.